1. Field of the Invention
This invention relates to an information signal reproducing apparatus, and more particularly, to an apparatus for reproducing information signals recorded in many recording tracks which are formed on a record bearing medium and spaced at a track pitch selected out of a plurality of different track pitches.
2. Description of the Related Art
In the following description, the apparatuses of the above-stated kind are exemplified by video tape recorders (hereinafter referred to as VTR's): The number of VTR's of the kind arranged to permit selection of a track pitch from different pitches have recently increased. The VTR of this kind is required to automatically shift the reproducing travel speed of the tape employed as a record bearing medium and/or the reproducing head according to the track pitch employed in recording. To meet this requirement, the VTR has been generally arranged to detect the track pitch from the reproduced frequency of a control (CTL) signal which is recorded at an edge part of the tape to indicate the track pitch employed. Meanwhile, in the case of the VTR arranged to perform tracking control in a manner called the four-frequency tracking control method, the track pitch is found, for example, by detecting the varying period of a tracking error signal.
In accordance with the above-stated conventional method, however, the frequency of the period of the signal used in finding the track pitch varies with the travelling speed of the tape. As a result, it has been possible for the VTR to detect the track pitch only in the case of normal reproduction. The VTR is used not only for normal speed reproduction but also for special speed reproduction such as slow motion reproduction, high speed search reproduction, etc. For the special reproducing operation, the tape travel speed is set at varied speeds. It has been, therefore, difficult to detect, at the time of special reproduction, the pitch at which the recording tracks are formed during recording. In order to make it possible, the VTR must be arranged to shift a circuit constant, a threshold value to be used for discrimination, etc., thereof every time the tape travel speed is changed. Such arrangement results in an extremely complex circuit arrangement.
Further, in the case of an arrangement for detect the track pitch on the basis of the varying period of the tracking error signal according to the four-frequency method, the varying period fluctuates according to the degree of linearity of the recording tracks. Accordingly, in case that the tracking error signal is obtained from reproduced pilot signals which are recorded at low levels and the track pitch is discriminated from the varying period of such low level signals, the track pitch tends to be erroneously detected.